AQA A Level Biology Paper 1 Markscheme [VERIFIED]

AQA A Level Biology Paper 1 Markscheme [VERIFIED] A experiment is reproducible if.... - ANSWER-....the results/pattern of your data matches the data of others .A vaccine can be used to produce immunity. Describe how memory cells are important in this process. (3) - ANSWER-important because when individual is in contact with virus again, antibodies can be produced at a faster rate in a secondary immune response, and so the pathogen can be destroyed faster. .abiotic - ANSWER-non-living .Alpha - ANSWER-Which type of glucose makes up starch? .Alpha and beta glucose - ANSWER-H and OH swapped on Carbon 1. .Amylopectin - ANSWER-Branched form of starch. More easily hydrolysed. .Amylose - ANSWER-Coiled, compact form of starch. Stored easily. .amylose and amylopectin - ANSWER-Names of two types of starch .artery structure - ANSWER-thick muscle layer so that they can dilate and contract to smooth blood flow. thick elastic layer so artery can stretch and recoil with systole and diastole, smoothing blood flow. overall thickness of wall is large so that it doesn't burst under pressure. .artificial active immunity - ANSWER-involves inducing an immune response in an individual WITHOUT them suffering the symptoms of the disease. e.g. vaccinations memory cells produced .Attaching lactase to the beads is a more efficient use of lactase than adding the lactase directly to cow's milk. Suggest three reasons why it is more efficient to attach lactase to the beads. - ANSWER-lactase bead can be reused continuous process lactase not present in milk .Benedict's test - ANSWER-Which food test is heated in a water bath? .Benedicts will turn from ........... to ........... in the presence of reducing sugars - ANSWER-blue to brick red .Beta - ANSWER-What type of glucose is cellulose made from? .biotic - ANSWER-living .Biuret is made up of... - ANSWER-equal volumes and copper sulphate and sodium hydroxide .Biuret will turn from ......... to ......... in the presence of proteins. - ANSWER-blue to purple .branched - ANSWER-Glycogen is.... .capillary structure - ANSWER-one cell thick endothelium. allows rapid diffusion. numerous, highly branched, so provides a larger surface area. narrow lumen and diameter. spaces in lining to allow tissue fluid to form. .courtship behaviour results in reproductive success by... - ANSWER-1. allowing recognition of own species 2. identifying those capable of breeding 3. forming a pair bond 4. synchronising mating .define community - ANSWER-all the populations of different species living and interacting in a particular place at the same time. .define ecological niche - ANSWER-The position occupied by an organism in a particular ecosystem, dependent upon the resources it uses. The more resources that are taken into account then the more carefully defined the organism's niche will be, the organism will become more specialised. .define ecology - ANSWER-the study of the inter-relationships between organisms and their environment, including abiotic and biotic factors. .define ecosystem - ANSWER-dynamic systems made up of a community and all the non-living factors of its environment. It includes all the living organisms that interact with one another and also with the physical and non-physical factors present. .define genome - ANSWER-the complete set of genes in a cell .define habitat - ANSWER-the place where an organism normally lives .define population - ANSWER-a group of individuals that occupy the same habitat at the same time and are potentially able to interbreed. .define proteome - ANSWER-the full range of proteins that a cell is able to produce .describe and explain the countercurrent exchange principle - ANSWER--the blood and the water flow in opposite directions -Maintains maximum diffusion gradient across all of gill. .describe and explain why plant stomata links to gas exchange and its benefits - ANSWER-stomata are like minute pores, on the underside of leaves. each has guard cells, which control the rate of gas exchange guard cells close when water loss is excessive .Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf (3) - ANSWER-it enters via stomata, which are opened as guard cells open. if diffuses down a concentration gradient through the air spaces. .Describe how oxygen in air in the alveoli enters the blood in capillaries. - ANSWER-diffusion across alveoli epithelium .describe humoral immunity - ANSWER-B cells take up antigens and present them. B cells activated by T-helper cells and form plasma cells. Plasma cells secrete antibodies and form memory cells. .describe the involvement of RER in producing chylomicrons - ANSWER-RER synthesises proteins in the ribosomes, which are needed to form chylomicrons. .describe the process of expiration - ANSWER-internal intercostals contract, external intercostals relax. ribs movie in and downwards. diaphragm relaxes. this decreases thorax volume air pressure in lungs becomes greater than atmospheric pressure, so air is forced out .describe the process of inspiration - ANSWER-external intercostals contract, internal intercostals relax. ribs move up and outwards, increasing thorax volume. diaphragm contracts, further increasing thorax volume air pressure in lungs becomes lower than atmospheric pressure, so air is forced in .describe the process of lipid digestion - ANSWER-in small intestine, bile salts combine with fat droplets and break them down smaller (emulsification). lipase enzymes from pancreas hydrolyse lipids into fatty acids, glycerol and monoglycerides. short chain fatty acids: diffuse directly into blood via epithelial cell longer chain fatty acids: combine with bile salts to form micelles, which break down into fatty acids and monoglycerides which diffuse into epithelial cells. once there, they recombine into triglycerides which can form chylomicrons. .describe the process of transcription - ANSWER-DNA unwinds and separates (H bond between bases broken) template strands form due to exposed bases free RNA nucleotides align with template strand through complimentary base pairing RNA polymerase bonds the nucleotides together, forming a molecule of mRNA complimentary to the DNA mRNA leaves nucleus via nuclear pore splicing occurs- introns removed .describe the process of translation - ANSWER-1. mRNA associates with a ribosome in the cytoplasm 2. tRNA molecules with complimentary anticodons align with the first 2 mRNA codons 3. peptide bond forms between the amino acid molecules 4. the tRNA that bound to the first codon is free to leave the ribosome 5. the ribosome moves along the mRNA by one codon and now a new tRNA with a complimentary anticodon enters the ribosome 6. this continues until the ribosome reaches a stop codon